Concentrating solar energy collector

ABSTRACT

Systems, methods, and apparatus by which solar energy may be collected to provide electricity, heat, or a combination of heat and electricity are disclosed herein.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/079,193 filed Apr. 4, 2011 and titled “Concentrating Solar EnergyCollector”, which claims priority to U.S. Provisional Patent ApplicationNo. 61/347,585 filed May 24, 2010 and titled “Concentrating Solar EnergyCollector” and to U.S. Provisional Patent Application No. 61/431,603filed Jan. 11, 2011 and also titled “Concentrating Solar EnergyCollector,” all of which are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The invention relates generally to the collection of solar energy toprovide electric power, heat, or electric power and heat.

BACKGROUND

Alternate sources of energy are needed to satisfy ever increasingworld-wide energy demands. Solar energy resources are sufficient in manygeographical regions to satisfy such demands, in part, by provision ofelectric power and useful heat.

SUMMARY

Systems, methods, and apparatus by which solar energy may be collectedto provide electricity, heat, or a combination of electricity and heatare disclosed herein.

In one aspect, a concentrating solar energy collector comprises alinearly extending reflector having a linear focus and a reflectivesurface that is or approximates a portion of a parabolic surface fromprimarily on one side of a symmetry plane of the parabolic surface, alinearly extending receiver oriented parallel to and located at orapproximately at the linear focus of the reflector and fixed in positionwith respect to the reflector, a support structure supporting thereflector and the receiver and pivotally mounted to accommodate rotationof the support structure, the reflector, and the receiver about arotation axis parallel to the linear focus of the reflector, and alinear actuator pivotally coupled to the support structure to rotate thesupport structure, the reflector, and the receiver about the rotationaxis. The reflective surface may be or approximate a portion of theparabolic surface from entirely on one side of the symmetry plane of theparabolic surface. The rotation axis may be oriented in an East-West orapproximately East-West direction, for example.

The receiver may comprise solar cells that, in operation of the solarenergy collector, are illuminated by solar radiation concentrated by thereflector onto the receiver. The receiver may additionally oralternatively comprise one or more coolant channels through which, inoperation of the solar energy collector, fluid may pass to collect heatfrom solar radiation concentrated by the reflector onto the receiver.

The solar energy collector may optionally comprise a drive shaftextending parallel to the rotation axis and mechanically coupled to thelinear actuator to transmit rotational motion of the drive shaft todrive the linear actuator. The linear actuator may be pivotally coupledto the drive shaft, and the drive shaft isolated from thrust loads onthe linear actuator.

The support structure may be pivotally mounted at a plurality of pivotpoints, in which case the linear actuator may be one of a plurality oflinear actuators each of which is located near a corresponding one ofthe pivot points and pivotally coupled to the support structure torotate the support structure, the reflector, and the receiver about thelinear actuator's corresponding one of the pivot points. One or moredrive shafts, optionally present, may extend parallel to the rotationaxis and be mechanically coupled to the linear actuators to transmitrotational motion of the drive shaft to drive the linear actuators. Thelinear actuators may be pivotally coupled to the drive shaft or shafts,and the drive shaft or shafts may be isolated from thrust loads on thelinear actuators.

The support structure may comprises a plurality of transverse reflectorsupports supporting the reflector and extending transverse to therotation axis, and a corresponding plurality of receiver supports eachconnected to and extending from, or approximately from, a single end ofa corresponding transverse reflector support to support the receiverabove the reflector. In such cases, the linear actuator may be pivotallycoupled to a transverse reflector support to rotate the supportstructure, the reflector, and the receiver about the rotation axis.Alternatively, the linear actuator may be pivotally coupled to areceiver support to rotate the support structure, the reflector, and thereceiver about the rotation axis.

The support structure may comprises a rotation shaft coincident with therotation axis and a lever arm attached to the rotation shaft, in whichcase the linear actuator may be pivotally coupled to the lever arm torotate the rotation shaft and thereby rotate the support structure, thereflector, and the receiver about the rotation axis.

The receiver may comprise upper and lower surfaces on opposite sides ofthe receiver, with the lower surface of the receiver located at orapproximately at the linear focus of the reflector and the upper surfaceof the receiver comprising solar cells arranged to face the sun when thesolar energy collector (e.g., the reflector and the receiver) isoriented to concentrate solar radiation on the lower surface of thereceiver. The solar cells of the upper surface of the receiver maygenerate sufficient electricity under a solar irradiance of at leastabout 100 Watts per square meter (W/m²) of solar cell, at least about150 W/m² of solar cell, at least about 200 W/m² of solar cell, at leastabout 250 W/m² of solar cell, at least about 300 W/m² of solar cell, atleast about 350 W/m² of solar cell, or at least about 400 W/m² of solarcell to power a drive system, including the linear actuator, coupled tothe support structure to rotate the support structure, the reflector,and the receiver about the rotation axis. If the receiver comprises oneor more coolant channels as described above, the solar cells of theupper surface may additionally, or alternatively, power one or morepumps that pump fluid through the coolant channels.

The reflector may comprise a plurality of linearly extending reflectiveelements oriented parallel to the linear focus of the reflector andfixed in position with respect to each other and the receiver, with thelinearly extending reflective elements arranged in two or more parallelside-by-side rows with each row including two or more of the linearlyextending reflective elements arranged end-to-end. In such cases, thesupport structure may comprise a plurality of separate longitudinalreflector supports each of which has a long axis oriented parallel tothe linear focus of the reflector and each of which comprises a channelportion parallel to its long axis, a first lip portion on one side ofand parallel to the channel portion, and a second lip portion parallelto and on an opposite side of the channel portion from the first lipportion. Each of the linearly extending reflective elements may beattached to and supported by the lip portions, and bridge the channelportion, of at least a corresponding one of the longitudinal reflectorsupports. Each row of linearly extending reflective elements may besupported by at least a first and a second of the longitudinal reflectorsupports arranged end-to-end with an end portion of the firstlongitudinal reflector support positioned within a flared end of thechannel portion of the second longitudinal reflector support.

In another aspect, a concentrating solar energy collector comprises alinearly extending reflector having a linear focus, a linearly extendingreceiver oriented parallel to the linear focus of the reflector andfixed in position with respect to the reflector, a support structuresupporting the reflector and the receiver and pivotally mounted toaccommodate rotation of the support structure, the reflector, and thereceiver about a rotation axis parallel to the linear focus of thereflector, and a drive system coupled to the support structure to rotatethe support structure, the reflector, and the receiver about therotation axis. The receiver comprises upper and lower surfaces onopposite sides of the receiver, with the lower surface of the receiverlocated at or approximately at the linear focus of the reflector and theupper surface of the receiver comprising solar cells arranged to facethe sun when the solar energy collector (e.g., the reflector and thereceiver) is oriented to concentrate solar radiation on the lowersurface of the receiver. The solar cells of the upper surface of thereceiver generate sufficient electricity under a solar irradiance of atleast about 100 Watts per square meter (W/m²) of solar cell, at leastabout 150 W/m² of solar cell, at least about 200 W/m² of solar cell, atleast about 250 W/m² of solar cell, at least about 300 W/m² of solarcell, at least about 350 W/m² of solar cell, or at least about 400 W/m²of solar cell to power the drive system.

The drive system powered by the solar cells on the upper surface of thereceiver may comprise, for example, one or more motors, one or moredrive shafts extending parallel to the rotation axis and driven by theone or more motors, one or more linear actuators driven by the one ormore drive shafts and coupled to the support structure to rotate thesupport structure, the reflector, and the receiver about the rotationaxis, and a controller that controls the motor and/or actuators.

The rotation axis may extend, for example in an East-West orapproximately (e.g., substantially) East-West direction.

If the receiver comprises one or more coolant channels as describedabove, the solar cells of the upper surface may additionally, oralternatively, power one or more pumps that pump fluid through thecoolant channels. Alternatively, such pumps if present may be powered byan energy source external to the solar energy collector.

The reflector may comprise a plurality of linearly extending reflectiveelements oriented parallel to the linear focus of the reflector andfixed in position with respect to each other and the receiver, with thelinearly extending reflective elements arranged in two or more parallelside-by-side rows with each row including two or more of the linearlyextending reflective elements arranged end-to-end. In such cases, thesupport structure may comprise a plurality of separate longitudinalreflector supports each of which has a long axis oriented parallel tothe linear focus of the reflector and each of which comprises a channelportion parallel to its long axis, a first lip portion on one side ofand parallel to the channel portion, and a second lip portion parallelto and on an opposite side of the channel portion from the first lipportion. Each of the linearly extending reflective elements may beattached to and supported by the lip portions, and bridge the channelportion, of at least a corresponding one of the longitudinal reflectorsupports. Each row of linearly extending reflective elements may besupported by at least a first and a second of the longitudinal reflectorsupports arranged end-to-end with an end portion of the firstlongitudinal reflector support positioned within a flared end of thechannel portion of the second longitudinal reflector support.

In another aspect, a concentrating solar energy collector comprises alinearly extending reflector having a linear focus, a linearly extendingreceiver oriented parallel to and located at or approximately at thelinear focus of the reflector and fixed in position with respect to thereflector, a support structure supporting the reflector and the receiverand pivotally mounted at a plurality of pivot points to accommodaterotation of the support structure, the reflector, and the receiver abouta rotation axis parallel to the linear focus of the reflector, and aplurality of linear actuators each of which is pivotally coupled to thesupport structure near a corresponding one of the pivot points to rotatethe support structure, the reflector, and the receiver about itscorresponding one of the pivot points.

The solar energy collector may optionally comprise a drive shaftextending parallel to the rotation axis and mechanically coupled to thelinear actuators to transmit rotational motion of the drive shaft todrive the linear actuators. The linear actuators may be pivotallycoupled to the drive shaft, and the drive shaft isolated from thrustloads on the linear actuators.

The receiver may comprise upper and lower surfaces on opposite sides ofthe receiver, with the lower surface of the receiver located at orapproximately at the linear focus of the reflector and the upper surfaceof the receiver comprising solar cells arranged to face the sun when thesolar energy collector (e.g., the reflector and the receiver) isoriented to concentrate solar radiation on the lower surface of thereceiver. The solar cells of the upper surface of the receiver maygenerate sufficient electricity under a solar irradiance of at leastabout 100 Watts per square meter (W/m²) of solar cell, at least about150 W/m² of solar cell, at least about 200 W/m² of solar cell, at leastabout 250 W/m² of solar cell, at least about 300 W/m² of solar cell, atleast about 350 W/m² of solar cell, or at least about 400 W/m² of solarcell to power a drive system, including the linear actuators, coupled tothe support structure to rotate the support structure, the reflector,and the receiver about the rotation axis. If the receiver comprises oneor more coolant channels as described above, the solar cells of theupper surface may additionally, or alternatively, power one or morepumps that pump fluid through the coolant channels.

The reflector may comprise a plurality of linearly extending reflectiveelements oriented parallel to the linear focus of the reflector andfixed in position with respect to each other and the receiver, with thelinearly extending reflective elements arranged in two or more parallelside-by-side rows with each row including two or more of the linearlyextending reflective elements arranged end-to-end. In such cases, thesupport structure may comprise a plurality of separate longitudinalreflector supports each of which has a long axis oriented parallel tothe linear focus of the reflector and each of which comprises a channelportion parallel to its long axis, a first lip portion on one side ofand parallel to the channel portion, and a second lip portion parallelto and on an opposite side of the channel portion from the first lipportion. Each of the linearly extending reflective elements may beattached to and supported by the lip portions, and bridge the channelportion, of at least a corresponding one of the longitudinal reflectorsupports. Each row of linearly extending reflective elements may besupported by at least a first and a second of the longitudinal reflectorsupports arranged end-to-end with an end portion of the firstlongitudinal reflector support positioned within a flared end of thechannel portion of the second longitudinal reflector support.

In another aspect, a concentrating solar energy collector comprises alinearly extending reflector having a linear focus, a linearly extendingreceiver oriented parallel to and located at or approximately at thelinear focus of the reflector and fixed in position with respect to thereflector, a support structure supporting the reflector and the receiverand pivotally mounted to accommodate rotation of the support structure,the reflector, and the receiver about a rotation axis parallel to thelinear focus of the reflector, a linear actuator extending transverse tothe rotation axis and pivotally coupled to the support structure torotate the support structure, the reflector, and the receiver about therotation axis, and a drive shaft extending parallel to the rotation axisand mechanically coupled to the linear actuator to transmit rotationalmotion of the drive shaft to drive the linear actuator. The linearactuator may be pivotally coupled to the drive shaft, and the driveshaft isolated from thrust loads on the linear actuator.

The receiver may comprise upper and lower surfaces on opposite sides ofthe receiver, with the lower surface of the receiver located at orapproximately at the linear focus of the reflector and the upper surfaceof the receiver comprising solar cells arranged to face the sun when thesolar energy collector (e.g., the reflector and the receiver) isoriented to concentrate solar radiation on the lower surface of thereceiver. The solar cells of the upper surface of the receiver maygenerate sufficient electricity under a solar irradiance of at leastabout 100 Watts per square meter (W/m²) of solar cell, at least about150 W/m² of solar cell, at least about 200 W/m² of solar cell, at leastabout 250 W/m² of solar cell, at least about 300 W/m² of solar cell, atleast about 350 W/m² of solar cell, or at least about 400 W/m² of solarcell to power a drive system, including the linear actuator, coupled tothe support structure to rotate the support structure, the reflector,and the receiver about the rotation axis. If the receiver comprises oneor more coolant channels as described above, the solar cells of theupper surface may additionally, or alternatively, power one or morepumps that pump fluid through the coolant channels.

The reflector may comprise a plurality of linearly extending reflectiveelements oriented parallel to the linear focus of the reflector andfixed in position with respect to each other and the receiver, with thelinearly extending reflective elements arranged in two or more parallelside-by-side rows with each row including two or more of the linearlyextending reflective elements arranged end-to-end. In such cases, thesupport structure may comprise a plurality of separate longitudinalreflector supports each of which has a long axis oriented parallel tothe linear focus of the reflector and each of which comprises a channelportion parallel to its long axis, a first lip portion on one side ofand parallel to the channel portion, and a second lip portion parallelto and on an opposite side of the channel portion from the first lipportion. Each of the linearly extending reflective elements may beattached to and supported by the lip portions, and bridge the channelportion, of at least a corresponding one of the longitudinal reflectorsupports. Each row of linearly extending reflective elements may besupported by at least a first and a second of the longitudinal reflectorsupports arranged end-to-end with an end portion of the firstlongitudinal reflector support positioned within a flared end of thechannel portion of the second longitudinal reflector support.

In another aspect, a concentrating solar energy collector comprises alinearly extending reflector having a linear focus, a linearly extendingreceiver oriented parallel to and located at or approximately at thelinear focus of the reflector and fixed in position with respect to thereflector, and a support structure supporting the reflector and thereceiver and pivotally mounted to accommodate rotation of the supportstructure, the reflector, and the receiver about a rotation axisparallel to the linear focus of the reflector. The reflector comprises aplurality of linearly extending reflective elements oriented parallel tothe linear focus of the reflector and fixed in position with respect toeach other and the receiver, with the linearly extending reflectiveelements arranged in two or more parallel side-by-side rows with eachrow including two or more of the linearly extending reflective elementsarranged end-to-end. The support structure comprises a plurality ofseparate longitudinal reflector supports each of which has a long axisoriented parallel to the linear focus of the reflector and each of whichcomprises a channel portion parallel to its long axis, a first lipportion on one side of and parallel to the channel portion, and a secondlip portion parallel to and on an opposite side of the channel portionfrom the first lip portion. Each linearly extending reflective elementis attached to and supported by the lip portions, and bridge the channelportion, of at least a corresponding one of the longitudinal reflectorsupports. Each row of linearly extending reflective elements issupported by at least a first and a second of the longitudinal reflectorsupports arranged end-to-end with an end portion of the firstlongitudinal reflector support positioned within a flared end of thechannel portion of the second longitudinal reflector support.

Optionally, in each row a single one of the linearly extendingreflective elements extends the length of the first longitudinalreflector support except for its flared end, and another single one ofthe linearly extending reflective elements extends the length of thesecond longitudinal reflector support and abuts an end of the linearlyreflective element supported by the first longitudinal reflectorsupport. The ordering of the first and second longitudinal reflectorsupports in adjacent rows may be opposite, so that gaps or jointsbetween the reflective elements in one row are not next to gaps orjoints between reflective elements in an adjacent row.

In another aspect, a concentrating solar energy collector comprises alinearly extending reflector having a linear focus and a reflectivesurface that is or approximates a portion of a parabolic surface fromentirely on one side of a symmetry plane of the parabolic surface, alinearly extending receiver oriented parallel to and located at orapproximately at the linear focus of the reflector and fixed in positionwith respect to the reflector, and a support structure supporting thereflector and the receiver and pivotally mounted at a plurality of pivotpoints to accommodate rotation of the support structure, the reflector,and the receiver about a rotation axis parallel to the linear focus ofthe reflector. The support structure comprises a plurality of transversereflector supports supporting the reflector and extending transverse tothe rotation axis, and a corresponding plurality of receiver supportseach connected to and extending from, or approximately from, a singleend of a corresponding transverse reflector support to support thereceiver above the reflector. The solar energy collector also comprisesa plurality of linear actuators each of which is located near acorresponding one of the pivot points and pivotally coupled to acorresponding one of the transverse reflector supports to rotate thesupport structure, the reflector, and the receiver about the linearactuator's corresponding one of the pivot points, and a drive shaftextending parallel to the rotation axis and mechanically coupled to thelinear actuators to transmit rotational motion of the drive shaft todrive the linear actuators. The linear actuators are pivotally coupledto the drive shaft, and the drive shaft is isolated from thrust loads onthe linear actuators. The rotation axis may be oriented in an East-Westor approximately East-West direction, for example.

The receiver may comprise solar cells that, in operation of the solarenergy collector, are illuminated by solar radiation concentrated by thereflector onto the receiver. The receiver may additionally oralternatively comprise one or more coolant channels through which, inoperation of the solar energy collector, fluid may pass to collect heatfrom solar radiation concentrated by the reflector onto the receiver.

The receiver may comprise upper and lower surfaces on opposite sides ofthe receiver, with the lower surface of the receiver located at orapproximately at the linear focus of the reflector and the upper surfaceof the receiver comprising solar cells arranged to face the sun when thesolar energy collector (e.g., the reflector and the receiver) isoriented to concentrate solar radiation on the lower surface of thereceiver. The solar cells of the upper surface of the receiver maygenerate sufficient electricity under a solar irradiance of at leastabout 100 Watts per square meter (W/m²) of solar cell, at least about150 W/m² of solar cell, at least about 200 W/m² of solar cell, at leastabout 250 W/m² of solar cell, at least about 300 W/m² of solar cell, atleast about 350 W/m² of solar cell, or at least about 400 W/m² of solarcell to power a drive system, including the linear actuators, coupled tothe support structure to rotate the support structure, the reflector,and the receiver about the rotation axis. If the receiver comprises oneor more coolant channels as described above, the solar cells of theupper surface may additionally, or alternatively, power one or morepumps that pump fluid through the coolant channels.

The reflector may comprise a plurality of linearly extending reflectiveelements oriented parallel to the linear focus of the reflector andfixed in position with respect to each other and the receiver, with thelinearly extending reflective elements arranged in two or more parallelside-by-side rows with each row including two or more of the linearlyextending reflective elements arranged end-to-end. In such cases, thesupport structure may comprises a plurality of separate longitudinalreflector supports each of which has a long axis oriented parallel tothe linear focus of the reflector and each of which comprise a channelportion parallel to its long axis, a first lip portion on one side ofand parallel to the channel portion, and a second lip portion parallelto and on an opposite side of the channel portion from the first lipportion. Each of the linearly extending reflective elements may beattached to and supported by the lip portions, and bridge the channelportion, of at least a corresponding one of the longitudinal reflectorsupports. Each row of linearly extending reflective elements may besupported by at least a first and a second of the longitudinal reflectorsupports arranged end-to-end with an end portion of the firstlongitudinal reflector support positioned within a flared end of thechannel portion of the second longitudinal reflector support.

In another aspect, a concentrating solar energy collector comprises alinearly extending reflector having a linear focus, a linearly extendingreceiver oriented parallel to and located at or approximately at thelinear focus of the reflector and fixed in position with respect to thereflector, a support structure supporting the reflector and the receiverand pivotally mounted to accommodate rotation of the support structure,the reflector, and the receiver about a rotation axis parallel to thelinear focus of the reflector, and a first solar radiation sensor that,when illuminated by solar radiation concentrated by the reflector,generates a signal by which rotation of the support structure, thereflector, and the receiver may be controlled to maximize concentrationof solar radiation onto the receiver. The first solar radiation sensormay be located, for example, in a focal region of the reflector.

The first solar radiation sensor may optionally comprises two solarradiation detectors positioned on opposite sides of a center line of thelinear focus of the reflector, each of which is optionally elongated ina direction transverse to the linear focus of the reflector.

The solar energy collector may also comprise a second solar radiationsensor positioned to be illuminated directly by solar radiation notconcentrated by the reflector. The second solar radiation sensor maygenerate a signal by which rotation of the support structure, thereflector, and the receiver may be controlled to illuminate the firstsolar radiation sensor with solar radiation concentrated by thereflector. The second solar radiation sensor may, for example, be fixedin position with respect to reflector and the receiver and located in aplane oriented perpendicular to an optical axis of the reflector.

The second solar radiation sensor may comprise, for example, a linearlyelongated gnomon and two linearly elongated solar radiation detectorspositioned on opposite sides of the gnomon, with the long axes of thegnomon and the linearly elongated solar radiation detectors arrangedparallel to the linear focus of the reflector.

In another aspect, a method of collecting solar energy comprisesorienting a concentrator to maximize or substantially maximizeconcentration of solar radiation onto a receiver through which a fluidis flowed to collect heat, thereby shading a surface underlying theconcentrator from direct solar radiation. The method further comprisesreorienting the concentrator to reduce the amount of solar radiationconcentrated on the receiver, while maintaining significant shading ofthe surface underlying the concentrator, when a temperature of the fluidexceeds a predetermined value.

The reoriented concentrator may block, for example, at least about 70%,about 80%, about 90%, or about 95% of the amount of solar radiation thatthe concentrator would block if oriented to maximize concentration ofsolar radiation onto the receiver. The predetermined temperature may be,for example, at least about 70° C., about 75° C. about 80° C., about 85°C., about 90° C., or about 95° C.

These and other embodiments, features and advantages of the presentinvention will become more apparent to those skilled in the art whentaken with reference to the following more detailed description of theinvention in conjunction with the accompanying drawings that are firstbriefly described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show an example solar energy collector.

FIG. 2 shows a graph of a parabolic surface and its symmetry plane, bywhich features of some solar energy collectors disclosed herein may bebetter understood.

FIGS. 3A-3D show perspective (3A), side (3B), and end (3C, 3D) views ofexamples of a linearly extending reflective element attached to andsupported by a longitudinal reflector support; FIG. 3E shows an end viewof linearly extending reflective elements attached to and supported by aportion of another example longitudinal reflector support, FIGS. 3F and3G show perspective views of reflectors attached to additional examplelongitudinal reflector supports, FIG. 3H shows a cross-sectional view ofthe longitudinal reflector supports of FIGS. 3F and 3G.

FIG. 4A shows a side view of the example solar energy collector of FIGS.1A-1C, absent its reflector, including details of a transverse reflectorsupport; FIG. 4B shows the portion of the example longitudinaltransverse reflector support of FIG. 3E supported by a portion of atransverse reflector support as shown, for example, in FIG. 4A, FIG. 4Cshows a top view of reflector/longitudinal reflector support assembliesof FIGS. 3F and 3G attached to transverse reflector supports.

FIGS. 5A-5C show an example arrangement for mounting a portion of areflector-receiver arrangement (e.g., module) of a solar energycollector on a rotation shaft.

FIGS. 6A and 6B show an example solar energy collector comprising threereflector-receiver modules sharing a rotation shaft.

FIGS. 7A and 7B show an example of three solar energy collectors gangedto be driven by a single actuator.

FIGS. 8A-8B show another example solar energy collector.

FIG. 9 shows an example arrangement of a transverse reflector supportand a receiver support used in the example solar energy collector ofFIGS. 8A, 8B, 11A, and 11B.

FIGS. 10A-10C show the example solar energy collector of FIGS. 8A and 8Boriented to concentrate solar radiation onto its receiver when the sunis directly overhead (10A), at −5 degrees from the vertical (in thedirection of the earth's equator), and at +60 degrees from the vertical(away from the equator).

FIGS. 11A-11B show another example solar energy collector.

FIGS. 12A-12C show the example solar energy collector of FIGS. 11A and11B oriented to concentrate solar radiation when the sun is directlyoverhead (10A), at −5 degrees from the vertical (in the direction of theearth's equator), and at +60 degrees from the vertical (away from theequator).

FIG. 13 shows another example solar energy collector.

FIGS. 14A-14B show the example solar energy collector of FIG. 13oriented to concentrate solar radiation onto its receiver when the sunis at −15 degrees from the vertical (in the direction of the earth'sequator), and at +65 degrees from the vertical (away from the equator).

FIGS. 15 a and 15 b show, respectively, example solar energy collectorscomprising five and six of the solar energy collectors of FIG. 13.

FIGS. 16A-16C show perspective, exploded, and cross-sectional views ofan example gear assembly that may be used to drive linear actuators insome example solar energy collectors disclosed herein.

FIG. 17 shows a portion of an example solar energy collector comprisingthe example gear assembly of FIGS. 16A-16C.

FIGS. 18A-18B show example arrangements of sun sensors that may be usedto control the orientation of some example solar energy collectorsdisclosed herein.

FIGS. 19A-19B show example reflective elements (e.g., mirrors) havinglaminated structures.

DETAILED DESCRIPTION

The following detailed description should be read with reference to thedrawings, in which identical reference numbers refer to like elementsthroughout the different figures. The drawings, which are notnecessarily to scale, depict selective embodiments and are not intendedto limit the scope of the invention. The detailed descriptionillustrates by way of example, not by way of limitation, the principlesof the invention. This description will clearly enable one skilled inthe art to make and use the invention, and describes severalembodiments, adaptations, variations, alternatives and uses of theinvention, including what is presently believed to be the best mode ofcarrying out the invention.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly indicates otherwise. Also, the term “parallel” is intended tomean “substantially parallel” and to encompass minor deviations fromparallel geometries rather than to require that parallel rows ofreflectors, for example, or any other parallel arrangements describedherein be exactly parallel.

This specification discloses apparatus, systems, and methods by whichsolar energy may be collected to provide electricity, heat, or acombination of electricity and heat. Solar energy collectors asdisclosed herein may be used, for example, in some variations of themethods, apparatus, and systems disclosed in U.S. patent applicationSer. No. 12/788,048, filed May 26, 2010, titled “Concentrating SolarPhotovoltaic-Thermal System,” incorporated herein by reference in itsentirety.

Referring now to FIGS. 1A-1C, an example solar energy collector 100comprises a linearly extending reflector 120, a linearly extendingreceiver 110 comprising a surface 112 located at or approximately at thelinear focus of the reflector and fixed in position with respect to thereflector, and a support structure 130 supporting the reflector and thereceiver and pivotally mounted to accommodate rotation of the supportstructure, the reflector, and the receiver about a rotation axis 140parallel to the linear focus of the reflector. In use, the supportstructure, reflector, and receiver are rotated about rotation axis 140to track the sun such that solar radiation incident on reflector 120 isconcentrated onto receiver 110, i.e., such that the optical axes ofreflector 120 are directed at the sun. (Any path perpendicular to thelinear focus of reflector 120 for which light rays traveling along thatpath are focused by the reflector onto the centerline of the receiver isan optical axis of reflector 120 and collector 100).

In the illustrated example, the reflective surface of reflector 120 isor approximates a portion of a parabolic surface. Referring now to thegraph in FIG. 2, a parabolic surface 132 may be constructedmathematically (in a coordinate space spanned by axes x, y, z, as shown,for example) by translating a parabola 134 along an axis 136 (in thisexample, the y axis) perpendicular to the plane of the parabola (in thisexample, the x, z plane). Symmetry plane 137 (the y, z plane in thisexample) divides parabolic surface 132 into two symmetric halves 132 a,132 b. The linear focus 138 of the parabolic surface is orientedperpendicular to the plane of the parabola and lies in symmetry plane137 at a distance F (the focal length) from the parabolic surface. Forparabolic reflective surfaces as in this example, the optical axes arein the symmetry plane of the surface and oriented perpendicularly to thelinear focus of the surface. In this example, the z axis is an opticalaxis of the reflector.

Referring again to FIGS. 1A-1C, in the illustrated example thereflective surface of reflector 120 is or approximates a portion of aparabolic surface taken entirely from one side of the symmetry plane ofthe parabolic surface (e.g., from 132 a or 132 b in FIG. 2, but notboth). In other variations, the reflective surface of reflector 120 isor approximates a portion of a parabolic surface taken from primarilyone side of the symmetry plane of the parabolic surface (e.g., more than50%, more than 60%, more than 70%, more than 80%, more than 90%, or morethan 95% of the reflective surface is from one side of the symmetryplane of the parabolic surface), but includes a portion of the parabolicsurface on the other side of the symmetry plane, as well.

Although reflector 120 is parabolic or approximately parabolic in theillustrated example, reflector 120 need not have a parabolic orapproximately parabolic reflective surface. In other variations of solarenergy collectors disclosed herein, reflector 120 may have any curvaturesuitable for concentrating solar radiation onto a receiver.

In the illustrated example, reflector 120 comprises a plurality oflinearly extending reflective elements 150 (e.g., mirrors) orientedparallel to the rotation axis and fixed in position with respect to eachother and with respect to the receiver. Linear reflective elements 150may each have a length equal or approximately equal to that of reflector120, in which case they may be arranged side-by-side to form reflector120. (Reflector 120 may have a length, for example, of about 5 meters toabout 12 meters, in some variations about 11.2 meters, in somevariations about 6 meters). Alternatively, some or all of linearreflective elements 150 may be shorter than the length of reflector 120,in which case two or more linearly extending reflective elements 150 maybe arranged end-to-end to form a row along the length of the reflector,and two or more such rows may be arranged side-by-side to form reflector120.

Linearly extending reflective elements 150 may each have a width, forexample, of about 8 centimeters to about 15 centimeters, and a length,for example, of about 1.2 meters to about 3.2 meters. In somevariations, some or all of reflective elements 150 have a width of about10.7 centimeters. In some variations, some or all of reflective elements150 have a width of about 13.2 centimeters. The widths of reflectiveelements 150 may vary with position in reflector 120. For example, insome variations reflective elements 150 located further away fromreceiver 110 are wider than reflective elements 150 located closer toreceiver 110 (see, e.g., FIG. 15B described below). Reflective elements150 may be flat, substantially flat, or curved (e.g., along a directiontransverse to their long axes to focus incident solar radiation).

Although in the illustrated example reflector 120 comprises linearlyextending reflective elements 150, in other variations reflector 120 maybe formed from a single continuous reflective element, from two or morereflective elements with a width perpendicular to the rotation axisgreater than their length along the rotation axis, or in any othersuitable manner.

Linearly extending reflective elements 150, or other reflective elementsused to form a reflector 120, may be or comprise, for example, anysuitable front surface mirror or rear surface mirror. The reflectiveproperties of the mirror may result, for example, from any suitablemetallic or dielectric coating or polished metal surface. Somevariations may utilize a mirror having a laminated structure asdescribed later in this specification. Some other variations may utilizea rear surface mirror formed with low-iron glass having a thickness ofabout 3 to about 4 millimeters.

Receiver 110 may comprise solar cells (not shown) located, for example,on receiver surface 112 to be illuminated by solar radiationconcentrated by reflector 120. In such variations, receiver 110 mayfurther comprise one or more coolant channels accommodating flow ofliquid coolant in thermal contact with the solar cells. For example,liquid coolant (e.g., water, ethylene glycol, or a mixture of the two)may be introduced into and removed from receiver 110 through manifolds(not shown) at either end of the receiver located, for example, on arear surface of the receiver shaded from concentrated radiation. Coolantintroduced at one end of the receiver may pass, for example, through oneor more coolant channels (not shown) to the other end of the receiverfrom which the coolant may be withdrawn. This may allow the receiver toproduce electricity more efficiently (by cooling the solar cells) and tocapture heat (in the coolant). Both the electricity and the capturedheat may be of commercial value.

FIGS. 1A and 1B also show optional coolant storage tank 115, pump 117,and controller 120. Coolant may be stored in tank 115 and pumped by pump117 from tank 115 to receiver 110 (through coolant conduits, e.g., notshown), through receiver 110, and back to tank 115. Pump 115 may becontrolled by controller 120 based, for example, on temperaturemeasurements of coolant entering and/or leaving receiver 110.

In some variations, the receiver comprises solar cells but lackschannels through which a liquid coolant may be flowed. In othervariations, the receiver may comprise channels accommodating flow of aliquid to be heated by solar energy concentrated on the receiver, butlack solar cells.

Solar energy collector 100 may comprise any suitable receiver. Inaddition to the examples illustrated herein, suitable receivers mayinclude, for example, those disclosed in U.S. patent application Ser.No. 12/622,416, filed Nov. 19, 2009, titled “Receiver For ConcentratingPhotovoltaic-Thermal System;” and U.S. patent application Ser. No.12/774,436, filed May 5, 2010, also titled “Receiver For ConcentratingPhotovoltaic-Thermal System;” both of which are incorporated herein byreference in their entirety.

In some variations, receiver 110 is the same length, or approximatelythe same length, as reflector 120 and centered length-wise overreflector 120 (e.g., the examples of FIGS. 8A and 11A). In somevariations, receiver 110 is shorter than reflector 120 and centeredlength-wise over reflector 120 (e.g., the examples of FIGS. 6A and 6B).In some variations receiver 110 is the same length, or approximately thesame length, as reflector 120 and positioned length-wise with respect toreflector 120 such that one end of receiver 110 extends beyond acorresponding end of reflector 120 (not shown). In some variations,receiver 110 is shorter than reflector 120, and positioned with one endapproximately in line with a corresponding end of reflector 120 (notshown). In the latter variations, the other end of receiver 110 does notextend to the other end of reflector 120.

In some variations, surface 112 of receiver 110 is tilted to facereflector 120. In the illustrated example, the reflective surface ofreflector 120 is or approximates a portion of a parabolic surface, andreceiver surface 112 is tilted away from an orientation that would makeit perpendicular to the symmetry plane of that parabolic surface byabout 45 degrees. In other variations, surface 112 may be tilted, forexample, at an angle of about 30 degrees to about 60 degrees from anorientation perpendicular to the symmetry plane. Surface 112 may also betilted to face reflector 120 in variations in which reflector 120 is notparabolic or approximately parabolic. In the illustrated example, theperiphery (edges) of surface 112 defines the optical aperture ofreceiver 110. In some variations, receiver 110 may absorb solarradiation on an internal surface, after the solar radiation passesthrough an optical aperture of the receiver. In such variations, theoptical aperture of receiver 110 (though not defined by an externalsurface as in the illustrated example) may be tilted to face reflector120 as just described for surface 112.

In some variations, support structure 130 supports receiver 110 aboveand off-center of reflector 120. In the illustrated example, thereflective surface of reflector 120 is or approximates a portion of aparabolic surface, and receiver 110 is located closer to the edge ofreflector 120 nearest the symmetry plane of the parabolic surface. Inother variations, receiver 110 may be supported above reflector 120 in adifferent location.

In some variations, in use, the receiver is illuminated by concentratedsolar radiation that under-fills the receiver. For example, more thanabout 80%, more than about 85%, more than about 90%, or more than about95% of the energy of the concentrated solar radiation may be incident onthe receiver in a region having a width (transverse to the long axis ofthe receiver) that is about 75%, about 80%, about 85%, about 90%, orabout 95% of the overall width of the receiver (or of that portion ofthe receiver comprising solar cells). In some variations at least about90%, or at least about 95% of the solar energy incident on the solarcells is concentrated on a central portion of the linear array of solarcells having a width, perpendicular to the long axis of the array ofsolar cells, of less than about 80% of the corresponding width of thelinear array of solar cells. Under-filling the receiver in this mannermay increase the efficiency with which concentrated solar radiation iscollected and converted to useful electricity or heat.

Such under-filling may be accomplished, for example, by selecting thewidth of linearly extending reflective elements 150 (and theirtransverse curvature, if they are not flat or substantially flat) toprovide the desired concentrated solar radiation intensity distributionon the illuminated receiver surface.

Referring again to FIGS. 1A-1C, in the illustrated example supportstructure 130 comprises a plurality of transverse reflector supports 155supporting the reflector and extending transverse to rotation axis 140and/or to a long axis of the reflector, and a plurality of receiversupports 160 each connected to and extending from an end, orapproximately an end, of a transverse reflector support to support thereceiver over the reflector. In the illustrated example, a singleunitary support structure comprises a transverse reflector support 155portion and a receiver support portion 160. In other variations,including examples described later in this specification (e.g., FIGS.8A-15B), a transverse reflector support and a receiver support may beseparate pieces attached to each other at, or approximately at, an endof the transverse reflector support. In yet other variations, any othersuitable structure may be used to support the reflector and thereceiver.

In the illustrated example, transverse reflector supports 155 incombination with receiver supports 160 form “C” shapes. In othervariations, transverse reflector supports 155 in combination withreceiver supports 160 may form, for example, “V” shapes, “L” shapes, orany other suitable geometry.

In the illustrated example, transverse reflector supports 155 areattached to a shaft 165 (also shown separately in FIG. 5C) pivotallysupported by bearings on support posts 170. Support posts 170 supportthe shaft 165 and other components of support structure 130 above a base175. Base 175 may be installed, for example, at ground level, on arooftop, or in any other suitable location. Base 175 is optional. Forexample, in some variations posts 170 may directly support components ofsupport structure 130 at or above ground level or on a rooftop, forexample.

In the illustrated example, rotation axis 140 is coincident with shaft165, which is located approximately under and parallel to an edge ofreflector 120 nearest receiver 110. In some variations, the reflectivesurface of reflector 120 is or approximates a portion of a parabolicsurface, and rotation axis 140 lies in the symmetry plane of theparabolic surface. In other variations, rotation axis 140 may be locatedelsewhere.

In the illustrated example, a linear actuator 180 comprising anextensible shaft 182 is mechanically coupled between a pivotal connector184 on base 175 and a pivotal connector 186 on a vertically extendinglever arm 188 attached to shaft 165. Linear actuator 180 may rotateshaft 165 (and hence reflector 120 and receiver 110) around rotationaxis 140 to track the motion of the sun by extending or retractingextensible shaft 182. In the absence of base 175, linear actuator 180may be coupled, for example, to a pivotal connector on or attached tothe ground, a rooftop, or a separate support structure. In somevariations, linear actuator 180 may be controlled, for example, by alocally positioned controller such as controller 120 shown in FIGS. 1Aand 1B.

Other variations, some of which are described below (e.g., FIGS. 8A-17),may utilize a differently positioned linear actuator to rotate reflector120 and receiver 110 around rotation axis 140. In some variationsdescribed below (e.g., FIGS. 13-17), the linear actuators are orcomprise lead screws driven by a shared drive shaft to rotate reflector120 and receiver 110 around rotation axis 140. Any other suitableactuators or mechanisms and mounting arrangements that allow receiver110, reflector 120, and support structure 130 to be rotated around arotation axis parallel to a linear focus of reflector 120 to track thesun may also be used.

Solar energy collector 100 as illustrated, and its variations asdescribed throughout this specification, may be arranged with rotationaxis 140 oriented in an East-West, or approximately East-West,direction. The solar energy collector may be positioned with thereceiver side of reflector 120 positioned closest to the earth's equatoror, in other variations, with the receiver side of reflector 120positioned away from the equator and closest to the earth's (North orSouth, depending on hemisphere) pole.

In such East-West orientations, the daily motion of the sun in the skymay require a rotation of reflector 120 and receiver 110 around rotationaxis 140 of, for example, less than about 90 degrees (e.g., less thanabout 70 degrees) to collect a valuable quantity of incident solarradiation during the course of a day. A rotation mechanism utilizing alinear actuator as illustrated, for example, may effectively andinexpensively accomplish such a range of motion. Utilizing a reflectivesurface that is or approximates a portion of a parabolic surface takenentirely or primarily from one side of the symmetry plane of theparabolic surface may provide a compact reflector that may be rotatedabout a rotation axis located close to supporting surfaces, particularlyin variations in which the rotation axis is near an edge of thereflector.

As described in more detail below, support structure 130 may compriselongitudinal reflector supports each of which has a long axis orientedparallel to the rotation axis 140 and each of which supports a linearlyextending reflective element 150, or a single row of linearly extendingreflective elements 150 arranged end-to-end. The linearly extendingreflective element or elements may be attached, for example, to an uppersurface of the longitudinal reflector support. Transverse reflectorsupports 155, if present, may support such longitudinal reflectorsupports, directly support mirrors or other reflective elements, orsupport some other intermediate structure that in turn supports mirrorsor other reflective elements.

Referring now to FIGS. 3A (perspective view), 3B (side view), and 3C(end or cross-sectional view), an example longitudinal reflector support250 comprises a channel portion 255 parallel to its long axis, a firstplanar lip portion 260 a on one side of and parallel to channel portion255, and a second planar lip portion 260 b parallel to and on anopposite side of channel portion 255 from the first lip portion 260 a.Linearly extending reflective elements 150 are attached to and supportedby lip portions 260 a, 260 b, and bridge channel portion 255, oflongitudinal reflector support 250. In other variations, lip portions260 a and 260 b need not be planar, as illustrated. Any suitable profileor shape for lip portions 260 a, 260 b may be used.

In the example illustrated in FIGS. 3A-3C, linearly extending reflectiveelements 150 are attached to lip portions 260 a, 260 b by adhesive orglue pads 265. The adhesive or glue pads may be spaced, for example, atintervals of about 0.2 meters under the reflective elements. In someother variations, linearly extending reflective elements 150 areattached to longitudinal reflector supports with a silicone adhesivesuch as, for example, DOW Corning® 995 Silicone Structural Sealant. Anyother suitable method of attaching the reflective elements to thelongitudinal reflector support may be used, including other adhesives orglues deployed in any other suitable manner, screws, bolts, rivets andother similar mechanical fasteners, and clamps or spring clips.

In the illustrated example, longitudinal reflector support 250 is about11.2 meters long, channel portion 255 extends the length of longitudinalreflector support 250 and is about 10.5 centimeters wide and about 3.5centimeters deep, and lip portions 260 a and 260 b extend the length oflongitudinal reflector support 250 and are about 2.0 centimeters wide.Linearly extending reflective elements 150 are about 10.7 centimeterswide in this example. In the example illustrated in FIGS. 1A-1C, eachlinearly extending reflective element is as long as reflector 120. Inother variations (e.g., the examples of FIGS. 3B, 8A, and 11A furtherdescribed below), two or more linearly extending reflective elements areattached end-to-end along a longitudinal reflector support with, forexample, a spacing of about 1 millimeter between reflective elements.

Individual longitudinal reflector supports as disclosed herein mayextend the length of the reflector. Alternatively, some or all of thelongitudinal reflector supports may be shorter than the overall lengthof the reflector, in which case two or more longitudinal reflectorsupports may be arranged end-to-end to form a row along the length ofthe reflector. Longitudinal reflector supports may have lengths thatallow them, for example, to be easily handled by an individual personand/or easily transported to, for example, a roof top on which a solarenergy collector is being assembled. Longitudinal reflector supports mayhave lengths, for example, of about 1.0 meters to about 3 meters, about1 meters to about 5 meters, about 1 meters to about 12.0 meters, about3.0 meters to about 5.0 meters, about 3 meters to about 12 meters, about5 meters to about 12 meters, about 2.8 meters, about 3.2 meters, andabout 6.0 meters. Channel portions 255 may be, for example, about 8centimeters to about 15 centimeters wide and about 2.0 centimeters toabout 8.0 centimeters deep. Lip portions 260 a, 260 b may be, forexample, about 1.0 centimeters to about 4.0 centimeters wide.

Referring now to FIG. 3D, in another example a longitudinal reflectorsupport 265 is substantially similar to longitudinal reflector support250 just described, except that longitudinal reflector support 265further comprises slot portions 270 a, 270 b at the ends of lip portions260 a, 260 b. In this example, linearly extending reflective elements150 may be loaded onto longitudinal reflector support 265 by sliding thereflective elements in from the end of the reflector support. Slotportions 270 a, 270 b help maintain linearly extending reflectiveelements 150 in position. Adhesives, glues, clamps, or mechanicalfasteners, for example, may be used to further secure the reflectiveelements to the reflector supports.

In the examples illustrated in FIGS. 3A-3D, the longitudinal reflectorsupports 250, 265 are trough shaped with a cross section having aflat-bottomed “U” shape. In other variations, the longitudinal reflectorsupports may be trough shaped with, for example, a rounded bottom “U”shape cross-section, a “V” shape cross-section, or an upside-down Ω(Greek letter Omega) cross-section. In other variations, thelongitudinal reflector support may comprise multiple channel portions(e.g., 2, 3, or more than 3), side-by-side in parallel, between lipportions 260 a and 260 b. In such variations, the longitudinal reflectorsupport may have, for example, a W shaped cross section or across-section that may be viewed as composed of multiple V or U shapesside-by-side.

Referring now to FIG. 3E (end or cross-sectional view), another examplelongitudinal reflector support 275 has the form of a corrugated sheet ofmaterial (e.g. a corrugated sheet of metal) comprising troughs 277 andcrests 279. Longitudinal reflector support 275 supports two or moreparallel rows of reflective elements 150. Reflective elements 150 may beattached to crests 279 with glue pads 265, for example. Each row ofreflective elements 150 may comprise a plurality of reflective elementsarranged end-to-end (e.g., as described above), or a single reflectiveelement extending the length of longitudinal reflector support 275. Insolar energy collectors 100 as described herein, a longitudinalreflector support 275 may be substituted, for example, for two or morelongitudinal reflector supports 250 or 265 supporting an equivalenttotal number of rows of reflective elements 150. Longitudinal reflectorsupports 275 may have lengths similar or the same as longitudinalreflector supports 250 and 265. The depth and width of troughs 270 maybe similar or equivalent to corresponding dimensions in longitudinalreflector supports 250 and 265.

Longitudinal reflector support 275 may comprise sufficient troughs 277and crests 279 to support all rows of reflective elements 155 in aparticular solar energy collector 100. Alternatively, a solar energycollector 100 may comprise two or more longitudinal reflector supports275. In the latter case, different longitudinal reflector supports 275may have troughs and crests dimensioned to accommodate linear reflectiveelements of different widths. A single longitudinal reflector support275 may, in some variations, include troughs of two or more sizes andcrests of two or more sizes to accommodate linear reflective elements oftwo or more different widths.

Referring now to FIGS. 3F-3H, some variations comprise one or morelongitudinal reflector supports 280 differing from those described sofar. Longitudinal reflector support 280 comprises a channel portion 255and lip portions 260 a, 260 b similar to previously describedvariations. However, longitudinal reflector support 280 differs frompreviously described variations in that at one end 281 a the channelportion 255 is flared outward compared to its dimensions along the restof its length and at its other end 281 b. One or more linearly extendingreflective elements 155 are attached to longitudinal reflector support280 similarly to as described above for other variations, except thatflared end portion 281 a is left uncovered by the reflective elements.As further described below with reference to FIG. 4C, two or more suchassemblies of longitudinal reflector support 280 and reflective elements155 may be arranged end to end with unflared end portions 281 b oflongitudinal support structures 280 positioned within flared endportions 281 a of adjacent longitudinal reflector supports 280. Theflared 281 a and unflared 281 b end portions of channels 255 may bedimensioned so that the outer surface of an unflared end portion 281 bfits closely within the inner surface of a flared end 281 a to allow foreasy mechanical coupling of adjacent in-line longitudinal reflectorsupports. In such an arrangement, the edges of linearly extendingreflective elements 155 supported by adjacent in-line longitudinalsupports 280 may abut (with an optional gap, for example, of about 1millimeter) to form a substantially continuous reflective surface.

Such variations may further include a longitudinal reflector support 282having the same general configuration as longitudinal reflector support280, except that both of its ends 281 b are unflared and one or morelinearly extending reflective elements 155 extend its full length.Either end 281 b of longitudinal reflector support 282 may be positionedwithin the flared end portion 281 a of an adjacent in-line longitudinalreflector support 280. A row of longitudinal reflector supports may thusinclude, for example, one or more longitudinal reflector supports 280arranged end-to-end followed by one longitudinal reflector support 282ending the row (see, e.g., FIG. 4C).

Longitudinal reflector supports 280, 282 may have lengths similar or thesame as longitudinal reflector supports 250 and 265 described above. Thedepth and width of channel portions 255 of longitudinal reflectorsupports 280, 282 may be similar or equivalent to correspondingdimensions in longitudinal reflector supports 250 and 265. Longitudinalreflector supports 280 and 282 as used in the same collector may be ofthe same length or of different lengths.

Longitudinal reflector supports may be formed, in some variations, fromsheet steel, sheet aluminum, or other sheet metals. In some variations,the lips and channel portion (and slot portions, if present) of alongitudinal reflector support as illustrated in FIGS. 3A-3D and 3F-3H,for example, may be rolled, folded, or otherwise formed from acontinuous piece of sheet metal. In some variations, the corrugatedstructure (e.g., troughs and crests) of a longitudinal reflector supportas illustrated in FIG. 3E, for example, may be rolled, folded, orotherwise formed from a continuous piece of sheet metal. In somevariations, longitudinal reflector supports as illustrated are formedfrom a continuous sheet of steel having a thickness of about 1millimeter.

Longitudinal reflector supports as disclosed herein may also be utilizedas suitable in any other solar energy collectors. For example,longitudinal reflector supports as disclosed herein may be used in solarenergy collectors as disclosed in U.S. patent application Ser. No.12/781,706, filed May 17, 2010, and titled “Concentrating Solar EnergyCollector,” which is incorporated herein by reference in its entirety.

As noted above, support structure 130 may comprise a plurality oftransverse reflector supports that extend away from the rotational axis140 and directly support mirrors or other reflective elements or,alternatively, support mirrors or reflective elements via longitudinalreflector supports as disclosed herein or via any other suitableadditional reflector support structure.

Referring now to FIGS. 1A-1C, and particularly to FIGS. 4A-4C, in theillustrated example transverse reflector supports 155 in solar energycollector 100 each comprise a notched edge 285. Portions of surfaces 300adjacent to the notches in transverse reflector supports 155 may be cutto define desired orientations of linearly extending reflective elementsto be supported by the transverse reflector supports. Each notch in anupper surface of a transverse reflector support 155 (e.g., FIGS. 4A-4C)corresponds to a separate row of one or more longitudinal reflectorsupports (e.g., 250, 265, 280, 282; FIGS. 3A-3D, 3F-3H) or to a separatetrough 277 or row of troughs 277 in one or more longitudinal reflectorsupports 275. Each notch in a transverse reflector support 155 isaligned with a similarly or identically placed notch (corresponding tothe same row of longitudinal reflector supports or troughs) in the othertransverse reflector support (or supports) in solar energy collector100. The channel portions 255 of the longitudinal reflector supports250, 265, 280, 282 (or the troughs 277 in longitudinal reflectorsupports 275) are positioned in corresponding notches of the transversereflector supports 155. The lip portions 260 a, 260 b of thelongitudinal reflector supports 250, 265, 280, 282 (or the crests 279 ofthe longitudinal reflector supports 275) are then in contact with andsupported by portions of surfaces 300 of the transverse reflectorsupports adjacent to the corresponding notches. Surfaces 300 may orientthe longitudinal reflector supports, and thus the linearly extendingreflective elements 150 they support, in a desired orientation withrespect to receiver 110 with a precision of about 0.5 degrees, forexample, or better (i.e., tolerance less than about 0.5 degrees). Inother variations, this tolerance may be, for example, greater than about0.5 degrees.

In the example of FIG. 4C, each longitudinal reflector support 280 or282 supports a single linearly extending reflective element 155,reflective elements supported by longitudinal reflector supports 282 arelonger than those supported by longitudinal reflector supports 280, andthe ordering of longitudinal reflector supports 280 and 282 reverses inadjacent rows. As a consequence, gaps or joints 375 between thereflective elements in one row are not next to gaps or joints betweenreflective elements in an adjacent row. Such staggering of gaps orjoints 375 may produce a more uniform illumination of the receiver bysolar radiation concentrated by reflector 120 than would occur if suchgaps or joints were generally next to gaps or joints in adjacent rows,because in the latter case such gaps or joints might cast shadows thatwere superimposed on each other on the receiver. Staggering of gaps orjoints 375, or of ends of rows of linearly extending reflective elements155, is further described at several points below.

Longitudinal reflector supports (e.g., 250, 265, 275, 280, 282) may beattached to transverse reflector supports 155 or to other portions ofsupport structure 130, for example, by welding, gluing, or use of anysuitable clamp, screw, bolt, rivet or other mechanical fastener. In somevariations, the longitudinal reflector supports are clamped at theirends (e.g., only at their ends) to another portion of support structure130.

As noted above, in the example illustrated in FIGS. 1A-1C and FIG. 4A, asingle unitary piece comprises a transverse reflector support 155 and areceiver support 160. In such variations, the unitary piece may beformed, for example, from continuous metal (e.g., steel, aluminum)sheets or plates into which the notches are cut or otherwise formed. Thetransverse reflector supports may be similarly fabricated in othervariations (e.g., FIGS. 8A-15B) in which the transverse reflectorsupport and receiver support are not parts of a unitary piece.

Although particular examples of longitudinal reflector supports andtransverse reflector supports are illustrated and described herein, anyother suitable reflector supports may be used in combination with theother elements of the solar energy collectors disclosed herein.

FIGS. 5A-5C show an example arrangement for pivotally mounting a portionof a reflector-receiver arrangement (e.g., a module) to a rotationshaft. In the illustrated example, longitudinal support bracket 305extends parallel to the linear focus of reflector 120 between transversereflector supports 155, to which it is attached. Longitudinal supportbracket 305 has, for example, an approximately 90 degree angledcross-section configured to complement a portion of a squarecross-section of shaft 165, to which it may be attached.

In addition, FIG. 5B shows an example in which linearly extendingreflective elements 150 are arranged so that their ends are staggered,i.e., lie at varying positions at the ends of reflector 120, as measuredparallel to the linear focus of the reflector. Such staggering may blurthe edges, created by the ends of reflector 120, of the linearlyextending concentrated solar radiation pattern focused on receiver 110by reflector 120, and consequently produce a more uniform illuminationof the receiver. In the illustrated example, the pattern at one end ofreflector 120 made by the staggered positions of reflective elements 150complements the pattern at the other end of reflector 120. This mayallow two or more identical or substantially identical such solar energycollectors to be aligned in parallel and adjacent to each other withadjacent staggered ends interleaved to form an approximately continuousreflective surface. In such cases, the gaps between linearly extendingreflective elements 150 from adjacent reflector structures will lie atvarying positions along the length of the reflector. This also mayproduce a more uniform illumination of the receivers. As evidenced bythe example of FIG. 5A, staggering of the ends of linearly extendingreflective elements is optional.

Solar energy collectors as disclosed herein may be modular, with two ormore identical or substantially similar modules, which might beindependent solar energy collectors, arranged to form a larger solarenergy collector. In the example of FIGS. 6A and 6B, a solar energycollector 310 comprises three of the example reflector-receiverarrangement (module) depicted in FIG. 5A (and utilized as well in theexample solar energy collectors of FIGS. 1A and 1B) arranged in line andadjacent to each other on a shared rotation shaft 165. In othervariations, two, or more than three, reflector-receiver modules may besimilarly arranged in line and adjacent to each other on a sharedrotation shaft.

Solar energy collectors as disclosed herein may also be arrangedside-by-side in parallel and ganged, i.e., driven by a shared drive(e.g., a linear actuator) to rotate around their respective rotationaxes to track the sun. Referring now to FIGS. 7A and 7B, for example, asolar energy collector 320 comprises three of the solar energycollectors of FIGS. 6A and 6B arranged side-by-side and in parallel anddriven by a single linear actuator 180. In the illustrated example, alinkage comprising push-pull bar 330 and lever arms 335 (a separate oneof which is coupled between the push-pull bar and each of the gangedsolar energy collectors) transfers the rotational motion of the solarenergy collector directly driven by the linear actuator to the othersolar energy collectors. In other variations two, three, or more thanthree solar energy collectors may be ganged in this or a similar manner.

FIGS. 8A-17 show several more examples of solar energy collectors andtheir components. Similarly to the previously illustrated examples,these additional example solar energy collectors comprise one or morelinearly extending receivers 110 comprising a surface 112 located at orapproximately at a linear focus of the reflector and fixed in positionwith respect to the reflector, and a support structure supporting thereflector and the receiver and pivotally mounted to accommodate rotationof the support structure, the reflector, and the receiver about arotation axis 140 parallel to the linear focus of the reflector. Thesupport structure, reflector, and receiver may be rotated about rotationaxis 140 to track the sun such that solar radiation incident onreflector 120 is concentrated onto receiver 110. Also similarly to theexample solar energy collectors described above, in these additionalexamples the reflective surface of the reflector may be or approximate aparabolic surface taken entirely, or primarily, from one side of thesymmetry plane of the parabolic surface. Receiver 110 may be tilted toface reflector 120, and may be positioned with respect to reflector 120,as in the solar energy collectors described above.

Generally, the individual components of the additional example solarenergy collectors, and their structure and arrangement, may be variedsimilarly or identically to as described above with respect to thepreviously illustrated examples. Some of the additional example solarenergy collectors (e.g., those shown in FIGS. 8A-12C) may be ganged aspreviously described, to allow a single actuator to simultaneously drive(rotate) two or more side-by-side rows of solar energy collectors. Inuse, the additional example solar energy collectors may beadvantageously oriented with rotation axis 140 along an East-Westdirection.

Referring now to FIGS. 8A and 8B, and also to FIG. 9, an example solarenergy collector 350 differs from the examples previously describedherein primarily in the structure and arrangement of transversereflector support 155 and receiver support 160, and in its rotationmechanism. Referring now to FIG. 9 in particular, in this exampletransverse reflector support 155 and receiver support 160 are formed asseparate pieces, rather than as parts of a single unitary piece aspreviously illustrated. Transverse reflector support 155 comprises atransverse support member 155 a supporting a plate 155 b. Plate 155 bcomprises a notched edge 285, with portions of surfaces 300 adjacent tothe notches cut (or otherwise formed) to define desired orientations oflinearly extending reflective elements to be supported by the transversereflector support. Receiver support 160 comprises a receiver mount (orbracket) 160 a at one end of a support member 160 b. The other end ofsupport member 160 b is attached to an end of transverse support member155 b.

As described with respect to previous examples, transverse reflectorsupport 155 may support longitudinal reflector supports 250 (as in FIG.8A), directly support mirrors or other reflective elements, or supportsome other intermediate structure that in turn supports mirrors or otherreflective elements.

Referring again to FIGS. 8A and 8B, each assembly of a transversereflector support 155 and a receiver support 160 is pivotally mounted,near the joint between support members 155 a and 160 b, to a support355. These pivot points are aligned to define rotation axis 140. Alinear actuator 180 comprising an extensible shaft 182 is mechanicallycoupled between a pivotal connector 184 on base 175 and a pivotalconnector 186 attached to transverse support member 155 a of atransverse reflector support 155. Linear actuator 180 may rotatetransverse reflector support 155, receiver support 160, and hencereflector 120 and receiver 110 around rotation axis 140 to track themotion of the sun by extending or retracting extensible shaft 182. Inthe absence of base 175, linear actuator 180 may be coupled, forexample, to a pivotal connector on or attached to the ground, a rooftop,or a separate support structure. Some variations utilize a singleactuator configured as illustrated to rotate reflector 120 and receiver110 around rotation axis 140, with the rotational motion transferred toother transverse reflector supports 155 by a longitudinal member 360extending parallel to the long axis of the reflector and attached toeach of the transverse reflector supports. Other variations may utilizeseveral such linear actuators, each coupled to a separate one of thetransverse reflector supports.

FIGS. 10A-10C show the example solar energy collector of FIGS. 8A and 8Boriented to concentrate solar radiation when the sun is directlyoverhead (FIG. 10A), at −5 degrees from the vertical in the direction ofthe earth's equator (FIG. 10B), and at +60 degrees from the verticalaway from the equator (FIG. 10C).

Referring now to FIGS. 11A and 11B, another example solar energycollector 370 differs from the example described in FIGS. 8A-10Cprimarily in its rotation mechanism. In this example, each assembly of atransverse reflector support 155 and a receiver support 160 is pivotallymounted, in a central region of support member 155 a, to a support 355.These pivot points are aligned to define rotation axis 140. A linearactuator 180 comprising an extensible shaft 182 is mechanically coupledbetween a pivotal connector 184 on base 175 and a pivotal connector 186attached to a receiver support member 160 b of a receiver support 160.Linear actuator 180 may rotate receiver support 160, transversereflector support 155, and hence reflector 120 and receiver 110 aroundrotation axis 140 to track the motion of the sun by extending orretracting extensible shaft 182. In the absence of base 175, linearactuator 180 may be coupled, for example, to a pivotal connector on orattached to the ground, a rooftop, or a separate support structure. Somevariations utilize a single actuator configured as illustrated to rotatereflector 120 and receiver 110 around rotation axis 140, with therotational motion transferred to other receiver support members 160 b bya longitudinal member 360 extending parallel to the long axis ofreflector 120 and attached to each of the receiver support members.Other variations may utilize several such linear actuators, each coupledto a separate one of the receiver support members.

FIGS. 12A-12C show the example solar energy collector of FIGS. 11A and11B oriented to concentrate solar radiation when the sun is directlyoverhead (FIG. 12A), at −5 degrees from the vertical in the direction ofthe earth's equator (FIG. 12B), and at +60 degrees from the verticalaway from the equator (FIG. 12C).

Referring now to FIG. 13, another example solar energy collector 400differs from the examples of FIGS. 8A-12C primarily in its rotationmechanism. In this example, each assembly of a transverse reflectorsupport 155 and a receiver support 160 is pivotally mounted, in acentral region of transverse reflector support 155, to a verticalsupport 355. These pivot points are aligned to define rotation axis 140.Linear actuators 405 each comprise a threaded rod 405 a and a threadedpivotal connector 405 b. Each threaded pivotal connector 405 b ispivotally mounted to a lever arm 410 attached to a transverse reflectorsupport 155. One end of each threaded rod 405 a engages itscorresponding threaded pivotal connector 405 b. The other end of eachthreaded rod 405 a is mechanically coupled to a corresponding gearassembly 415 pivotally connected to a lower portion of vertical support355. A drive shaft 420 extending parallel to the long axis of reflector120 drives each threaded rod 405 a via its corresponding gear assembly415. Threaded rods 405 a may be driven to move threaded pivotalconnectors 405 b either toward or away from vertical supports 355 andthereby rotate transverse reflector supports 155, receiver supports 160,and hence reflector 120 and receiver 110 around rotation axis 140 totrack the motion of the sun.

FIGS. 14A-14B (end views) show the example solar energy collector ofFIG. 13 oriented to concentrate solar radiation when the sun is at −15degrees from the vertical in the direction of the earth's equator (FIG.14A) and at +65 degrees from the vertical away from the equator (FIG.14B). In the illustrated example, these orientations represent the endsof the travel range for linear actuators 405, with all angularorientations in between accessible. In other variations, linearactuators 405 may be arranged to provide rotation over different (e.g.,greater or lesser) angular ranges as desired.

As with other solar energy collectors previously described herein, solarenergy collectors 400 shown in FIG. 13 and FIGS. 14A-14B may be used asmodules from which larger solar energy collectors may be assembled. Inthe example of FIG. 15 a, a solar energy collector 499 comprises five ofthe solar energy collectors 400 arranged in line and adjacent to eachother, mechanically coupled, and sharing a single drive shaft 420 thatdrives all of linear actuators 405. Other variations may comprise two,three, four, or more than five of the solar energy collectors 400 soarranged. In the illustrated example, drive shaft 420 is in turn drivenby a motor 425 centrally located along solar energy collector 499. Insome variations, solar energy collector 499 comprises two drive shafts,each driven by motor 425, extending in opposite directions from motor425 along the long axis of solar energy collector 499 to drive differentsets of linear actuators 405. FIG. 15B similarly shows a solar energycollector 498 comprising six of the solar energy collectors 400 arrangedin line and adjacent to each other, mechanically coupled, and sharing adrive shaft that drives linear actuators 405.

In the examples illustrated in FIGS. 13-15 b, solar energy collectors400, 498, and 499 each comprise a linear actuator 405 (arranged torotate reflector 120 and receiver 110) for each pivot point defined bythe pivotal connection between a transverse reflector support 155 and avertical support 355, with all of the linear actuators 405 in a solarenergy collector driven by a shared drive shaft 420. In othervariations, however, more or fewer linear actuators than pivot pointsmay be used. Also, in other variations more than one drive shaft may beused, with each drive shaft driving a different set of linear actuators.

More generally, in some variations a solar energy collector (e.g., solarenergy collector 498 or 499) is assembled from two or more (e.g.,identical or substantially identical) modules, each of which includes atransverse reflector support 155 and associated longitudinal reflectorsupport or supports. In some such variations, where the solar energycollector includes N modules, it may include N+1 pivot points (i.e., onebetween each module and one at each end of the solar energy collector),with a linear actuator associated with each pivot point to rotate thereflector and receiver around the solar energy collector's rotationaxis. The number of modules N may be, for example, 1, 2, 3, 4, 5, 6, 7,8, 9, 10, or more than 10. The linear actuators may be driven by one ormore shared drive shafts extending along the long axis of the solarenergy collector.

One advantage to associating a separate linear actuator with each pivotpoint is that the solar energy collector need not be as resistant totorsion (twisting around its long axis) as would be necessary if fewerdrive mechanisms than pivot points were used. Hence the solar energycollector may be of lighter construction than otherwise, and moresuitable for rooftop deployment, for example. In addition, as explainedin more detail below, gear assemblies 415 (e.g., as shown in FIGS. 13-15a) may be arranged so that the thrust load from the linear actuators405, resulting from forces exerted to rotate the reflector and receiverassembly, is decoupled from drive shafts 420 and instead borne byvertical supports 355. This allows the load resulting from rotation ofthe reflector and receiver assembly to be easily distributed across alarge area beneath the solar energy collector, through the (e.g., N+1)vertical supports 355, rather than concentrated at only a small numberof locations (e.g., at the ends of a long rotation shaft). Such a broadload distribution beneath the solar energy collectors may also beadvantageous, for example, when the solar energy collectors areinstalled on rooftops or similar locations.

Solar energy collectors 400, 498, and 499 differ from example solarenergy collectors previously described herein by including (optional)angled cross brace 435 extending between an upper portion of onevertical support 355 and a lower portion of an adjacent vertical support435. Solar energy collector 400, 498, and 499 further differ fromexample solar energy collectors previously described herein by including(optional) angled cross brace 440 extending transversely to the longaxis of the solar energy collector between an upper portion of verticalsupport 355 and base 175, on the opposite side of vertical support 355from its associated linear actuator 405.

In FIG. 15 a, solar energy collector 499 is shown attached to andsupported by an (optional) support structure 445 comprising horizontallyoriented cross members 450 supported by vertical supports 455. Baseportions of solar energy collectors 400 and 499 may be attached to crossmember portions of support structure 445 using U-bolts 460 (FIG. 13),for example, or any other suitable connectors. Support structure 445 maybe arranged such that its vertical supports 455 align with or areotherwise appropriately located with respect to load bearing elements ofan underlying structure such as a roof, for example. Support structure445 thus serves as an adaptor between any underlying structure and thesolar energy collector it supports. Similar support structures may beused in combination with the other example solar energy collectorsdescribed herein.

FIGS. 16A-16C illustrate details of an example gear assembly 415 thatmay be employed in some variations of solar energy collectors disclosedherein (e.g., FIGS. 13-15 b) to drive linear actuators that rotate areflector/receiver assembly around a rotation axis to track the sun. Asexplained below, in operation a portion of gear assembly 415 pivotsaround drive shaft 420 to accommodate rotation of the reflector/receiverassembly to which it is mechanically coupled by lead screw 405 a. Asalso explained below, gear assembly 415 decouples the thrust load onlead screw 405 a from drive shaft 420 and may instead transmit thatthrust load directly to stationary support structure of the solar energycollector. FIGS. 16A-16C illustrate one example of a gear assembly 415providing these functions. Other variations of gear assembly 415providing such functions may also be advantageously employed in thesolar energy collectors described herein.

Referring now to FIGS. 16A-16C, a portion of drive shaft 420 internal togear assembly 415 is coupled via couplers 465 to external portions ofdrive shaft 420 (not shown in FIGS. 16A-16C). Pinion gear 470 of gearassembly 415 is mounted coaxially on and rotates with drive shaft 420.Bevel gear 475 is mounted coaxially on the end of and rotates with leadscrew 405 a, which is arranged at a 90 degree angle to drive shaft 420.Pinion gear 470 engages bevel gear 475 to transmit rotational motion ofdrive shaft 420 to lead screw 405 a. Lead screw 405 a engages a threadedpivotal connector (e.g., 405 b shown in FIG. 13) attached to areflector/receiver assembly in the solar energy collector to transmitforces collinearly with the axis of lead screw 405 a to thereflector/receiver assembly and thereby rotate the reflector/receiverassembly about one or more coaxial pivot points (see, e.g., FIG. 13).Rotation of drive shaft 420 in one direction or the other about its axisthus drives rotation of the reflector/receiver assembly in one directionor the other about its pivot points.

In the illustrated example, gear assembly 415 comprises a front bracket480 (including front wall 480 a and side walls 480 b) and rear brackets485 enclosing gears 470, 475, and a portion of drive shaft 420. Leadscrew 405 a is laterally supported by bushing 490 as it passes throughan opening in the front wall of bracket 480. Similarly, drive shaft 420is laterally supported in the side walls 480 b of bracket 480 bybearings 495 rotatably contacting bushings 500. In addition tosupporting bearings 495, bushings 500 also laterally support drive shaft420 as it passes through openings in rear brackets 485.

Thrust loads on lead screw 405 a are transmitted by thrust bearings 505from lead screw 405 a to the front wall 480 a of bracket 480 and thenceto the side walls 480 b of bracket 480. Thrust loads carried by sidewalls 480 b of bracket 480 are transmitted via bearings 495 and bushings500 to rear brackets 485. The thrust loads on lead screw 405 a are thusisolated from drive shaft 420 by thrust bearings 505, bushings 500, andbrackets 480 and 485. Rear brackets 485 may be mounted on stationarysupport structure of the solar energy collector using optional bolts510, for example.

In operation, bearings 495 rotatably contacting bushings 500 allow frontbracket 480, lead screw 405 a, and bevel gear 475 to pivot around driveshaft 420 as drive shaft 420 drives rotation of a reflector/receiverassembly around its pivot points.

FIG. 17 shows gear assembly 415 as just described in position in anexample solar energy collector.

Referring again to FIGS. 13-15B, solar energy collectors 400, 498, and499 differ from example solar energy collectors previously describedherein by including (optional) solar cells 430 on an upper surface ofreceiver 110. Solar cells 430 are arranged so that they face the sunwhen reflector 120 and receiver 110 are oriented to concentrate solarradiation on lower surface 112 of receiver 110. Solar cells 430 generateelectric power from solar radiation directly incident on them ratherthan concentrated on them by reflector 120. Other solar energycollectors described herein, as well as solar energy collectorsdescribed in U.S. patent application Ser. No. 12/788,048, filed May 26,2010, titled “Concentrating Solar Photovoltaic-Thermal System,” may alsooptionally include similarly arranged solar cells to generate electricpower from solar radiation not concentrated by the reflectors.Alternatively, or in addition, solar cells may be similarly arranged onor attached to portions of the support structure of such solar energycollectors to generate electric power from solar radiation notconcentrated by the reflector.

Electric power generated by solar cells 430 may be used, for example, toaugment an electric power output from receiver 110 generated usingconcentrated solar radiation. Alternatively, or in addition, electricpower generated by solar cells 430 may be used to power or partiallypower the solar energy collector's control systems, drive motors, orboth. In the latter cases, solar cells 430 may allow the solar energycollector to operate autonomously, i.e., to power itself rather thandraw power from the grid.

In some such autonomous variations of solar energy collectors, thenumber, efficiency, and/or area of solar cells 430 is sufficient togenerate sufficient electricity under a solar irradiance of at leastabout 100 Watts per square meter (W/m²) of solar cell, at least about150 W/m² of solar cell, at least about 200 W/m² of solar cell, at leastabout 250 W/m² of solar cell, at least about 300 W/m² of solar cell, atleast about 350 W/m² of solar cell, or at least about 400 W/m² of solarcell to power the solar energy collector's drive system. The drivesystem may include, for example, linear actuators, drive shafts, and ormotors that rotate the reflector and receiver, a control system thatcontrols such motors and actuators, and an optional sun tracking system(e.g., see below) that provides information to the control system toallow the control system to orient the reflectors and receivers tocollect solar energy. In some variations, solar cells 430 generatesufficient electricity to also power one or more pumps (and anyassociated control system including, e.g., temperature sensors) thatcirculate coolant through the receiver. In other variations, the drivesystem is powered by solar cells 430, but coolant pumps and associatedpump control systems are powered by an external source of electricity.In the latter variations, the pumps may be controlled and powered, forexample, by an application or user of the heated coolant.

Such autonomous systems may include solar cells on the lower surface ofthe receiver and thus generate electricity and collect heat (in thecoolant) from concentrated solar radiation. Alternatively, suchautonomous systems may be thermal—only. That is, some such autonomoussystems may lack solar cells on the lower surface of the receiver, usethe output of solar cells 430 primarily or only to power the drivesystems and (optionally) pumps and pump controllers, and provide onlycollected heat (in the form of heated coolant) as an output. In suchthermal-only variations, lower surface 112 of receiver 110 may becoated, painted (e.g., black), or otherwise treated to increase itsabsorption of solar radiation.

Any of the autonomous solar energy collectors just described may beoptionally configured to receive electric power from an external powersource as necessary for maintenance, repair, or other service of thesolar energy collector, or as backup power in the event the solar cellsfail or otherwise provide insufficient power, while still relyingexclusively on power from solar cells 430 for routine operation.Alternatively, any of the autonomous solar energy collectors justdescribed may be optionally configured to receive electric power from anexternal power source for routine operation, and rely on the solar cellsfor back-up power in the event the external power source fails orotherwise delivers insufficient power. In the latter cases, autonomousoperation occurs when the external primary source of power fails.

Autonomous solar energy collectors as just describe may beadvantageously implemented with an East-West rotation axis. In suchconfigurations, the reflector/receiver orientation used at the end ofone day's collection of concentrated solar radiation is near to theorientation required at the beginning of the next day. Consequently, atthe end of one day of autonomous operation solar cells 430 will be leftin position to approximately face the sun at the beginning of the nextday's operation, reducing the number and efficiency of solar cells 430required to power the solar energy collector at start-up and through theday.

Any of the solar energy collectors disclosed herein may (but need notnecessarily) include one or more sun sensors used to determine theorientation of the reflector in the solar energy collector (e.g., of itsoptical axis) with respect to the position of the sun. This informationmay be used to control the orientation of the reflector to optimize orotherwise adjust the amount of solar radiation concentrated by thereflector onto the solar energy collector's receiver. Examples of suchsun sensors are described next.

In the schematic illustration of FIG. 18A, solar energy collector 600may be identical or similar, for example, to any of the solar energycollectors described above. In addition to components previouslydescribed, however, solar energy collector 600 comprises a fine sunsensor 605 positioned in the focal region of reflector 120. Fine sunsensor 605 may be positioned in the plane of the front surface of areceiver 110 for example, as shown in FIG. 18B. When illuminated bysolar radiation (indicated by rays 607) concentrated by reflector 120,fine sun sensor 605 produces a signal or signals from which theorientation of the reflector 120/receiver 110 assembly can be determinedwith respect to the sun with sufficient precision to allow thatorientation to be adjusted as desired. In some variations, fine sunsensor 605 allows determination of the orientation of the reflector120/receiver 110 assembly with respect to the position of the sun with aprecision, for example, of or within about ±0.1 degrees.

Referring again to FIG. 18B as well as to FIG. 18A, in some variationsfine sun sensor 605 comprises two solar radiation detectors 605 a, 605 bpositioned in the plane of the front surface of receiver 110. Detectors605 a, 605 b are positioned on opposite sides of the center of thelinear focus of the reflector, each extending transversely with respectto the long axis of the receiver and the linear focus of the reflector.Detectors 605 a, 605 b may be, for example, linearly elongatedtransversely with respect to the long axis of the receiver. In thisarrangement, if the reflector 120/receiver 110 assembly is optimallyaligned with the sun to maximize collection of solar radiation (i.e.,with the optical axis of reflector 120 directed at the sun), detectors605 a, 605 b will detect solar radiation of particular magnitudes andproduce signals indicating those magnitudes. If the reflector120/receiver 110 assembly is misaligned with respect to optimalorientation but one or both of detectors 605 a, 605 b are stillilluminated by concentrated solar radiation, the signals provided bydetectors 605 a, 605 b will indicate the magnitude and direction ofmisalignment. For example, misalignment in one direction may increasethe signal provided by one of the detectors and decrease the signalprovided by the other. Hence the orientation of the reflector120/receiver 110 assembly with respect to the sun can be determined bycomparing signals from detectors 605 a, 605 b so long as one or both ofthe detectors are illuminated by solar radiation concentrated byreflector 120. Any suitable method or apparatus for comparing thesignals from detectors 605 a, 605 b may be used.

Detectors 605 a, 605 b may be or comprise solar cells, for example. Thesolar cells may be, for example, of the same type as those used inreceiver 110 and/or solar cells 430. Any other suitable solar radiationdetectors may be used instead, however. Also, any other suitableimplementation or configuration of a fine sun sensor 605 illuminated bysolar radiation concentrated by reflector 120 may also be used in placeof that just described.

As illustrated in FIG. 18A, solar energy collectors as disclosed hereinmay also include an optional coarse sun sensor 610. Coarse sun sensor610 may be positioned above or on an upper surface of receiver 110 in aplane oriented perpendicularly to the optical axis of reflector 120, forexample, as shown. Any other suitable position and orientation forcoarse sun sensor 110 may also be used. When illuminated directly bysolar radiation (indicated by rays 612), coarse sun sensor 110 producesa signal or signals from which the orientation of the reflector120/receiver 110 assembly can be determined with respect to the sun withsufficient precision to allow that orientation to be adjusted asdesired. In some variations also utilizing fine sun sensor 605, coarsesun sensor 110 allows the orientation of the reflector 120/receiver 110assembly with respect to the sun to be measured with sufficientprecision to adjust that orientation to illuminate fine sun sensor 605with solar radiation concentrated by reflector 120. That precision maybe, for example, of or within about ±5 degrees, ±3 degrees, ±2 degrees,or ±1 degree. Fine sun sensor 605 may then be used to further optimizethe orientation of reflector 120/receiver 110.

In the illustrated example, coarse sun sensor 610 comprises two linearlyelongated solar radiation detectors 610 a, 610 b positioned one oneither side of a linearly elongated gnomon 615 (shading structure), withthe long axes of detectors 610 a, 610 b and gnomon 615 arranged parallelto each other and to the rotation axis of the solar energy collector.Gnomon 615 is oriented perpendicular to the plane of detectors 610 a,610 b, and parallel to the optical axis of reflector 120. In thisarrangement, if the reflector 120/receiver 110 assembly is optimallyaligned with the sun to maximize collection of solar radiation, gnomon615 will be aligned directly at the sun and will cast no shadow. Ifinstead the reflector 120/receiver 110 assembly is aligned away from theoptimum for collecting solar radiation, gnomon 615 will shade one ofsolar radiation detectors 610 a, 610 b. The magnitudes of signalsprovided by detectors 610 a, 610 b thus indicate the magnitude anddirection of misalignment of the reflector 120/receiver 110 assembly.Hence, similarly to as described for fine sun sensor 605, theorientation of the reflector 120/receiver 110 assembly can be determinedby comparing signals from detectors 610, 610 b. Any suitable method andapparatus for comparing the signals from detectors 610 a, 610 b may beused.

Detectors 610 a, 610 b may be or comprise solar cells, for example. Thesolar cells may be of the same type as those used in receiver 110 and/orsolar cells 430. Any other suitable solar radiation detectors may beused, however. Also, any other suitable implementation or configurationof a coarse sun sensor 610 may also be used in place of that justdescribed.

In some variations, signals from a coarse sun sensor 610 as describedabove are used to control the orientation of the reflector 120/receiver110 assembly to adjust that orientation to illuminate a fine sun sensor615 as described above. Signals from fine sun sensor 615 are then usedto control further adjustment of the orientation of the reflector120/receiver 110 assembly to, for example, maximize collection of solarradiation.

Some other variations do not utilize a coarse sun sensor. Some of thosevariations measure an absolute orientation of the reflector 120/receiver110 assembly (e.g., using accelerometers), compare that orientation to acalculated position of the sun, and adjust the orientation of thereflector 120/receiver 110 assembly to illuminate a fine sun sensor 615as described above. Signals from fine sun sensor 615 may then be used aspreviously described.

Some variations using a coarse sun sensor 610 in combination with a finesun sensor 605 additionally measure an absolute orientation of thereflector 120/receiver 110 assembly (e.g., using accelerometers),compare that orientation to a calculated position of the sun, and adjustthe orientation of the reflector 120/receiver 110 assembly to a range inwhich coarse sun sensor 610 effectively or more effectively providessignals with which the orientation may be further adjusted to illuminatefine sun sensor 605 with concentrated solar radiation.

In addition to and as a consequence of collecting solar energy, solarenergy collectors generally shade the area beneath them from the sun.This is particularly true, for solar energy collectors as describedherein, when the reflector/receiver assembly is oriented to optimallycollect solar radiation, or at nearby orientations. In some variationsin which a solar energy collector is located on a building rooftop, forexample, the orientation of the reflector/receiver assembly may beadjusted to reduce or stop collection of concentrated solar radiation bythe receiver but continue to reflect a significant portion of incidentsolar radiation away from the roof and thereby provide significantshading of the underlying rooftop. For example, the reoriented reflector(more generally, concentrator) may block at least about 70%, about 80%,about 90%, or about 95% of the amount of solar radiation that it wouldblock if oriented to maximize concentration of solar radiation onto thereceiver. Such an orientation may be selected to provide maximum shadewithout overheating or otherwise damaging the receiver, for example.Such defocusing may be done, for example, on occasions in which thesupply or temperature of coolant available to cool the receiver isinsufficient to otherwise prevent overheating the receiver. For example,such defocusing may de done when the receiver, or a coolant in thereceiver, reaches or exceeds a predetermined temperature of, forexample, at least about 70° C., about 75° C. about 80° C., about 85° C.,about 90° C., or about 95° C.

In variations employing one or more sun sensors to control theorientation of the reflector/receiver assembly, a defocused orientationmay in addition be selected to maintain the reflector/receiver assemblyin an orientation in which the one or more sun sensors can providesignals with which to return the reflector/receiver assembly to anorientation that maximizes or substantially maximizes concentration ofsolar energy on the receiver. For example, in variations employingcoarse and fine sun sensors as described above, a defocused orientationmay in addition be selected to maintain the reflector/receiver assemblyin an orientation in which the coarse sun sensor can detect the positionof the sun and effectively provide signals with which the orientationmay be further adjusted to illuminate the fine sun sensor withconcentrated solar radiation.

Maintaining significant shading of an underlying roof, as justdescribed, effectively provides a “white roof” that may advantageouslykeep the building on which the solar energy collector is located coolerthan would otherwise be the case.

As noted above, in some variations a reflector 120 comprises linearreflective elements arranged end-to-end in rows (e.g., of equal length)along the length of the reflector, with two or more such rows arrangedside-by side (see, e.g., FIGS. 8A, 11A, and 15B). In such variations,and as illustrated, the linear reflective elements may be of two or moredifferent lengths and arranged such that gaps or joints 375 between thereflective elements in one row are not next to gaps or joints betweenreflective elements in an adjacent row. In some variations, no gaps orjoints between reflective elements in any row are next to gaps or jointsbetween reflective elements in any adjacent row. In some variations, themajority of gaps or joints between reflective elements in any row arenot adjacent to gaps or joints between reflective elements in anyadjacent row. Arrangements such as those just described may produce amore uniform illumination of the receiver by concentrated solarradiation than would occur if gaps or joints between reflective elementsin rows were generally next to gaps or joints in adjacent rows.

Also as noted above, in some variations linearly extending reflectiveelements 150 have a laminated structure. Referring to FIG. 19A, in theillustrated example reflective element 150 comprises a low-iron glasslayer 720 having a first surface 722 and a second surface 723. In use ina solar energy collector as disclosed herein, reflective element 150 isoriented so that surface 722 faces the receiver (and hence also theincident solar radiation). A reflective layer 725 is disposed on thesecond surface of the low-iron glass layer. An adhesive layer 730 isdisposed on the reflective layer. A second glass layer 735 is attachedby adhesive layer 730 to reflective layer 725.

In the example illustrated in FIG. 19B, reflective layer 725 is absentfrom edge portions (e.g., around the entire periphery of reflectiveelement 150) of the second surface 723 of low-iron glass layer 720.Adhesive layer 730 attaches corresponding edge portions (e.g., aroundthe entire periphery of reflective element 150) of second glass layer735 directly to the exposed edge portions of surface 723, and attachesother portions of second glass layer 735 to reflective layer 725. Inthis example, adhesive layer 730, in combination with glass layers 720and 735, may seal and/or protect reflective layer 725 from the externalenvironment.

Low-iron glass layer may be, for example, about 0.5 millimeters to about3 millimeters thick. Reflective layer 725 may comprise, for example,silver, gold, chrome, or any other suitable metal or non-metal materialor materials and be, for example, about 20 nanometers to about 200nanometers thick. Adhesive layer 725 may comprise, for example, anacrylic closed-cell foam adhesive tape (e.g., VHB™ tape available from3M™), and be, for example, about 0.5 millimeters to about 1.5millimeters thick. Second glass layer 735 may comprise, for example,soda lime glass or borosilicate glass and be, for example, about 2millimeters to about 5 millimeters thick. In one example, low-iron glasslayer 720 is about 1 millimeter thick, reflective layer 725 comprisessilver and is about 80 nanometers thick, adhesive layer 730 comprisesacrylic closed-cell foam tape and is about 0.9 millimeters thick, andsecond glass layer 735 comprises soda lime glass and is about 4millimeters thick.

Reflective layer 725 may be deposited and patterned (e.g., its edgesremoved), and adhesive layer 730 deposited, by conventional processes,for example.

Any of the above described variations of solar energy collectors mayoptionally be provided with spray nozzles, or the equivalent, located onthe receiver 110 or the receiver support 160, for example, andconfigured to spray a washing fluid (e.g., water) onto reflector 120 towash the reflector.

This disclosure is illustrative and not limiting. Further modificationswill be apparent to one skilled in the art in light of this disclosureand are intended to fall within the scope of the appended claims. Forexample, a shared hydraulic or pneumatic drive system driving two ormore (hydraulic or pneumatic) linear actuators may, in some variations,be substituted for a shared drive shaft driving two or more linearactuators as described herein.

What is claimed is:
 1. A concentrating solar energy collectorcomprising: a linearly elongated reflector having a linear focus; alinearly elongated receiver oriented parallel to and located at orapproximately at the linear focus of the reflector and fixed in positionwith respect to the reflector; and a support structure supporting thereflector and the receiver and pivotally mounted to accommodate rotationof the support structure, the reflector, and the receiver about arotation axis parallel to the linear focus of the reflector; wherein thereceiver comprises solar cells that, in operation of the concentratingsolar energy collector, are illuminated by solar radiation concentratedby the reflector onto the receiver; wherein the reflector comprises aplurality of linearly elongated reflective elements each having a longaxis, and the linearly elongated reflective elements are arranged on andattached to a sheet of metal in two or more parallel side-by-side rowswith the long axes of the linearly elongated reflective elements and therows oriented parallel to the linear focus of the reflector, the sheetof metal providing longitudinal support parallel to the rotation axisalong the length of the linearly elongated reflective elements; andwherein each row of linearly elongated reflective elements includes twoor more of the linearly elongated reflective elements arrangedend-to-end such that gaps or joints between the linearly elongatedreflective elements in each row are not next to gaps or joints betweenlinearly elongated reflective elements in an adjacent row.
 2. Theconcentrating solar energy collector of claim 1, wherein the linearlyelongated reflective elements are of two or more different lengths. 3.The concentrating solar energy collector of claim 2, wherein in each rowof linearly elongated reflective elements arranged end-to-end each gapor joint between linearly elongated reflective elements is separatedfrom its nearest neighbor gap or joint in the other rows of linearlyelongated reflective elements by at least one row of linearly elongatedreflective elements.
 4. The concentrating solar energy collector ofclaim 1, wherein the receiver comprises one or more coolant channelsthrough which, in operation of the concentrating solar energy collector,fluid may pass to collect heat from solar radiation concentrated by thereflector onto the receiver.
 5. The concentrating solar energy collectorof claim 1, wherein: the support structure comprises a plurality oftransverse reflector supports to which the sheet of metal is attached;each transverse reflector support extends transversely to the rotationaxis to support the reflector; and upper surfaces of the transversereflector supports orient the sheet of metal, and thus the linearlyelongated reflective elements attached to it, in a desired orientationwith respect to the receiver.
 6. The concentrating solar energycollector of claim 1, wherein the reflector has a parabolic curvaturetransverse to its long axis.
 7. The concentrating solar energy collectorof claim 1, wherein the linearly elongated reflective elements are flator substantially flat transverse to their long axes.
 8. Theconcentrating solar energy collector of claim 1, wherein: the receivercomprises one or more coolant channels through which, in operation ofthe concentrating solar energy collector, fluid may pass to collect heatfrom solar radiation concentrated by the reflector onto the receiver;the linearly elongated reflective elements are flat or substantiallyflat transverse to their long axes; and the support structure comprisesa plurality of transverse reflector supports to which the sheet of metalis attached, the transverse reflector supports supporting the reflectorand extending transverse to the rotation axis.
 9. The concentratingsolar energy collector of claim 8, wherein the linearly elongatedreflective elements are of two or more different lengths.
 10. Theconcentrating solar energy collector of claim 9, wherein in each row oflinearly elongated reflective elements arranged end-to-end each gap orjoint between linearly elongated reflective elements is separated fromits nearest neighbor gap or joint in the other rows of linearlyelongated reflective elements by at least one row of linearly elongatedreflective elements.